Injection syringe



F 41952 D. M: M LINTOCK INJECTION SYRINGE 2 SHEETS-SHEET 1 Filed Feb.25, 1948 ,o o 1/ 1 F 4 n 0 4' 1 u 3 3 8 1 @Mw Jn J fl T m AGENT 1952 D.M. M LINTOCK INJECTION SYRINGE 2 SI-IEETS--SHEET 2 I Filed Feb. 25, 1948I nv enl0r Duncan Menzies McLznioc/C treated with care betweeninjections.

Patented Feb. 12, 1952 UNITED STATES TENT OFFICE Application February25, 1948, Serial No. 10,682 In Great Britain January 16, 1947 Section 1,Public Law 690, August 8, 1946 Patent expires January 16, 1967 Claims.

This invention relates to injection syringes, namely intradermic orhypodermic syringes, of the type comprising a cylinder forming areceptacle'for a fluid to be injected into or under the skin of a bodyand a plunger in the cylinder, the plunger extending from the cylinderand being adapted to be pressed into the cylinder in order to ejecttherefrom a dose of the fluid.

The invention is especially although not exclusively concerned withinjection syringes used by veterinary surgeons, for example to giveinjections to cattle. These syringes are frequently used underconditions which call for what might be termed rough and ready handling;for example, when a veterinary surgeon is using a syringe to giveinjections to cattle in bad light, as is the case in many cowsheds.Thus, it is often impracticable to ensure that a syringe will be Errorsin judgment on the part of the surgeon may lead to seriously wrongdosage of the cattle.

An object of this invention is to provide a syringe of the type statedwhich will be capable of use with precision and reliability under eventhe worst conditions met with in a veterinary surgeon's practice, afeature of the invention being an improved mechanism whereby the actionof depressing the plunger to eject a dose from the cylinderautomatically sets the syringe in readiness for the next dose.

Another object of the invention is to provide an injection syringe ofthe type stated in which the plunger is associated with a manuallydepressible member in telescopic relation with the plunger and in whichmeans on the frame of the syringe guide said member and limit it todepressive and return axial movements of definite size,

corresponding to a dose.

Another object is to provide a plunger that is hollow, the manuallydepressible member to be formed as a ratchet-toothed rod extending witha sliding fit into the plunger.

Examples of injection syringes embodying the invention will now bedescribed with reference to the accompanying drawings.

Fig. 1 is a side elevation of an injection syringe.

comprises a cylinder I0 forming a receptacle for the fluid to beinjected and a plunger II extending slidably from the interior of thecylinder. The injector of the syringe as usual is a fine-bore tubularneedle I2 (Fig. 1 only) which in the example is secured by a nut I3 to afine-bore cap I4 screwed into the bottom end of the cylinder I I). Thecylinder forms a part of the syringes frame, another part of which is asupport in the form of an open cylindrical casing consisting of sidelimbs I5 and I6 and two end pieces II and I8. The bottom end piece I! isinternally screwthreaded, being screwed upon the head IilA of thecylinder It. A gland HA is screwed into the cylinder head IOA. The opencasing and plunger are fitted with ratchet-and-pawl mechanism thatpermits the plunger to be depressed step-by-step, each stepcorresponding to a dose of the fluid to be injected.

In the example, the plunger II is hollow and has its upper end open toreceive a component of the ratchet-and-pawl mechanism. The component isin effect the ratchet; it is a rod I9 which is in telescopic relationwith the plunger, being a neat sliding fit in the hollow portion 20 ofthe plunger, and which has ratchet-teeth 2| in the form of a series ofcircular ridges with intermediate grooves. Each ridge has the form of adownwardly directed tooth. The ratchetrod I9 is supported at its upperend 22 by a bearing in the top end piece I8 of the open casing, thebearing serving as a guide for the rod I9.

The ratchet-rod I9 is slidable up and down in said bearing to a shortextent, the top and bottom limits of its sliding movement being definedby a stop collar IBA on the rod l9 and a stop ISA upstanding from thebearing piece I8. The stop I8A is engageable by a cap 23 at the top ofthe ratchet-rod I9. The cap 23 bears against a small hand lever 24 whichis fulcrumed at 25 to a bracket 26 at the top of the partly open casingand which is movable up and down, the upper limit of its movement beingdefined by the point of engagement between the butt 24A of the lever andthe bracket 26. A return spring 2'! is interposed between the bearingpiece I8 and the cap 23 of the ratchet-rod. The arrangement is such thatthe hand lever 24 can be depressed to slide the ratchet-rod IS a shortbut definite stepdownwards and that when the hand lever is released theratchet-rod will be returned with the hand lever by the spring action.

The pawl component of the mechanism includes a block 28 forming theplunger head. On this head, at opposite sides, two spring-pressed pawls29 and 30 are pivotally mounted. One of these, namely the pawl 29, isthe pawl proper or driver of the mechanism, being engaged by the ratchetteeth 2| through a recess 3I in the plunger head 23. The arrangement issuch that when the ratchet-rod is depressed, the pawl 29 and the plungerII are forced to move a st p downwards. The other pawl 30 is a detent,or stop-pawl; it cooperates with a series of teeth 32 on the limb I5 ofthe open casing and serves to maintain the plunger I I in position aftereach depression, so that when the ratchet-rod I9 returns upwards aftermaking each step, the plunger does not return. That is to say, in theoperation of the syringe, the plunger II moves step-by-step downwardsfrom the internal ratchet-rod I9. The two pawls 29 and 30 are formedwith finger grips 33 by which they can be simultaneously pressed fromthe associated teeth 2I and 32, thus enabling the user of the syringe touse the pawls as a handgrip in order to withdraw the plunger to thestart of its range of movement.

One of the limbs I5 and I6 of the open casing may be marked with agraduated scale to indicate the number of doses contained in thecylinder. In the example, the syringe is designed to hold twenty doses,and the ratchet-and-pawl mechanism is designed to impart twenty steps tothe plunger, the teeth 2I and 32 being all spaced apart to an extentcorresponding to a single dose. Therefore, an appropriate scale toindicate the number of doses ejected, if any, comprises the numbers 0,5, l0, l5 and 20 marked on the limb IS in line with the teeth 32cooperating with the detent 35. There may be an extra scale on the limbI5 marked in reverse order 20, 15, 10, 5 and 0 to indicate the number ofdoses still contained in the syringe.

In use of the syringe, assuming that it is filled, in order to make aninjection of a dose of liquid the user inserts the needle I2 into orthrough the skin of the user and depresses the hand lever 24, whichreturns under the spring action leaving the syringe automatically setfor injection of the next dose.

The syringe according to the example, by virtue of the features ofconstruction herein described, has certain advantages namely:

The plunger being encased within the frame parts I5 to I8 is safeguardedeven when fully withdrawn against lateral pressure so that there is norisk that the plunger may become bent, or skewed, in the cylinder, ahappening which would lead to slackness in the fit of the plunger andexcessive friction; and such slackening of the plunger fit is highlyundesirable in an instrument required to give precise doses. Moreover,slackening of the plunger fit and excessive friction are avoided by themanner in which the force clue to depression of the hand lever 24 istransmitted to the plunger, namely, through the ratchet-rod I9 which isa component separate from the plunger and which is independently guidedaxially of the plunger by the bearing I8 and which gives axial guidanceand support to the plunger. Moreover, slackening of the plunger fit andexcessive friction are avoided by having the line of action of the lever24 and also the centre of the action of the stop I8A in the axis of theplunger; it will be manifest that if the lever acted at an inclinationon the plunger or if the stop were offset from the plunger agis,

distortion of the instrument when heavy pressure was applied wouldresult.

There is no practical risk that the plunger will be inadvertentlydepressed with resultant loss of fluid and reduction of the size of thenext dose. That is to say, the plunger itself is safeguarded by theframe parts IE to I8 from inadvertent pressure, and depression of thelever 24 is opposed by the spring 27. At the worst, inadvertentdepression of the lever 24 would lead to the loss of a single dose.Thus, the instrument is distinguished from any previously known syringewhose plunger is exposed and can by pressure inadvertently be applied toit be depressed throughout the entire length of the cylinder.

The arrangement of the hand lever is such that, without adding to theoverall width of the instrument, it gives a substantial mechanicaladvantage to the person making an injection; in the example, theadvantage is about 3 to l.

The syringe according to the example has various other features, namely:

To facilitate a steady hold of the syringe, it is provided with'theusual wings 3 2 (lugs projecting laterally from opposite limbs I5 and I6of the casing) and these wings are extended downwards along the casingand outturned with tails 35 at their lower ends, so that they provide agrip which, in combination with the hand lever 24, enables the user togrip the syringe firmly by his fingers, to exert a push-pull action andoperate the syringe easily and steadily simply by exerting pressure atthe root of his thumb on the hand lever. In addition, one of the wings34 has a thumb-piece 36 to facilitate manipulation of the syringe. It isof considerable importance to the work of injecting cattle, because ofthe. toughness of the skin into the structure of which the injectionmust be made and because the pressure to be exerted is oftenconsiderable, that the veterinary surgeon should be able with ease andfirmness to manipulate the syringe and also exert the necessary push. Heis enabled to do so by virtue of the combined hand lever 24- and holdingmeans 34, 35 and 36 provided in the syringe according to the example.

To ensure a satisfactory sliding fit of the plunger I I in the cylinderI0, including complete sealing against leakage, the cylinder head IDA isformed with an annular packing recess into the top of which the gland HAis screwed. A packing ring 31 is held in the recess by this gland. Thepacking ring is circular in cross-section. The arrangement is such thatthe plunger II can be entirely withdrawn from the cylinder I0 andreinserted with ease and. without injuring the packing.

In the modification according to Figs. 4, 5, 6 and '7, a syringe has anadjustment device by virtue of which the size of the doses can be variedto any of a range of sizes. In the device as illustrated, there are foursizes, for any selected one of which the device can be set.

The adjustment device comprises a castellated collar 38 which rests uponthe bearing piece I8 of the open casing and which provides a seat forthe spring 27 that presses upon the cap 23 of the ratchet-rod I9, theupper end 22 of which is slidable through the bearing piece. The collar38 is rotatable by hand into any one of four available positions, apart.Each of these positions is defined by one of four holes 39 in the collarwhich are engageable one at a time by a spring-pressed ball 4-0 in thebracket 26 to which the hand lever 24 is fulcrumed at 25.

There are four castellations 4| M 4| and 4|" of progressively differentheights, and the lever 24 has a foot 42 which abuts against one of thesecastella'tions whenever the hand lever 24 is fully depressed. Theratchet rod 19 has much finer teeth 43 than in the syringe according toFigs. 1 to 3, the teeth 43 being so spaced that four of them correspondto the maximum size dose to be had when the collar 38 is set so that thelowest castellation 41 will be contacted by the foot 42. In Fig. 4, thecollar 38 is set for the second largest dose, the castellation 4| beingin the contact position. Thus it will be seen that each castellation,when appropriately positioned, functions as a stop that determines theextent that the plunger can be pressed into the cylinder of the syringein order to inject a dose of the fluid.

In Figs. 7, the teeth 44 with which the detent 33 cooperates on the limb15 are finely spaced similarly to the teeth 43. syringe is the same asshown in Figs. 1 to 3, and corresponding parts are indicated by the samereference characters.

I claim:

1. An injection syringe comprising a cylinder to receive a fluid, aninjector on the cylinder, a support on the cylinder, a guide on saidsupport, a hollow plunger in the cylinder and extending therefrom inassociation with said support, wings on the support formed withoutturned tails, the wings and tails being engageable by the fingers ofthe user of the instrument to effect push-pull action, a rod memberextending through said guide and into the hollow plunger, ratchet-teethon said rod member, a spring-pressed pawl on said plunger engaged bysaid ratchet-teeth, a hand-operable lever member fulcrumed on saidsupport, being depressible by the hand of the user and being arranged todepress said rod member, pawl and plunger to cause ejection of a dose offluid from said cylinder and through said injector, a spring interposedbetween said support and said rod member to return the rod member andlever member following each depression thereof, correspondingratchet-teeth on said support, a spring-pressed detent on said plungerengaging said corresponding ratchet-teeth and. thus holding the plungerand pawl against return with the rod member, an adjustable stop deviceinterposed between said support and said lever member, said devicepresenting at different levels a plurality of stops individuallycontactible by one of said lever and rod members and serving todetermine the size of each dose, and means for holding said device inits position of adjustment.

2. An injection syringe comprising a cylinder to receive a fluid, aninjector on the cylinder, 2. plunger extending from the cylinder andbeing adapted when depressed to eject therefrom through the injector adose of the fluid, means on the cylinder for depressing the plunger,ratchet-and-pawl mechanism applied to the plunger to limit thedepression thereof to definite steps, an adjustable stop device on thecylinder, said device presenting at different levels a plurality ofstops individually contactible by said depressing means and serving todetermine the size of each dose, and means for holding said device inits position of adjustment.

3. An injection syringe comprising a frame, a cylinder connected withthe frame to receive a fluid, an injector on the cylinder, a plungerextending from the cylinder and being adapted In other respects, the awhen depressed to eject therefrom through the injector a dose of thefluid, manually depressible means on the frame for depressing theplunger, ratchet-and-pawl mechanism interposed between said depressiblemeans and the frame on the one hand and the plunger on the other hand totransmit successive depressions of said means to said plunger as steps,each step representing one dose, an adjustable stop device on saidframe, said device presenting at different levels a plurality of stopsindividually contactible by said depressible means and serving todetermine the size of each of said steps, and means for holding saiddevice in its position of adjustment.

4. An injection syringe comprising a cylinder to receive a fluid, aninjector on the cylinder, a support on the cylinder, a guide on saidsupport, a hollow plunger in the cylinder and extending therefrom inassociation with said support, wings on the support formed withoutturned tails, the wings and tails being engageable by the fingers ofthe user of the instrument to effect push-pull action, a rod memberextending through said guide and into the hollow plunger, ratchet-teethon said rod member, a spring-pressed pawl on said plunger engaged bysaid ratchet-teeth, a hand-lever member fulcrumed on said support, saidlever member being depressible by the hand of the user and beingarranged to depress said rod member, pawl and plunger to cause ejectionof a dose of fluid from said cylinder and through said injector, a stopon said support for engagement by one of said two members in order tolimit the depression of said rod member, a spring interposed betweensaid support and said rod member to return the rod member and levermember following each depression thereof, corresponding ratchet-teeth onsaid support, and a spring-pressed detent on said plunger engaging saidcorresponding ratchetteeth and thus holding the plunger and pawl againstreturn with the rod member.

5. An injection syringe comprising a cylinder assembly including acylinder to receive a fluid, an injector on the cylinder assembly, ahollow plunger in the cylinder and extending therefrom, a rod extendinginto the hollow plunger, ratchetteeth on said rod, a pawl on saidplunger engaged by said ratchet-teeth, hand means on said cylinderassembly depressible by the hand of a user of the syringe and beingarranged to depress said rod, pawl and plunger to cause ejection of adose of fluid from said cylinder and through said injector, said handmeans, rod, pawl and plunger constituting a depressible assembly, springmeans interposed between said support and said rod to return the rod andhand means following each depression thereof, and an adjustable stopdevice interposed between said two assemblies, said device presenting atdifferent levels a plurality of stops individually contactible by a partof one of said two assemblies and serving to determine the size of eachdose.

6. An injection syringe comprising a frame, a cylinder connected withthe frame to receive a fluid, an injector on the cylinder, a hollowplunger extending from the cylinder and being adapted when depressed toeject therefrom through the injector a dose of the fluid, an actuatingmember on the frame for depressing said plunger, ratchet-and-pawlmechanism interposed between the actuating member and frame on the onehand and the plunger on the other hand, said mechanism including aratchet-toothed member that extends into the plunger and forms a one-wayoperative connection therewith, a stop device on said frame, said devicebeing contactible by one of said two members, namely the actuatingmember and the ratchet-toothed member, and serving to determine the sizeof each dose.

'7. An injection syringe as claimed by claim 6 in which theratchet-and-pawl mechanism comprises two pawls mounted on the plunger,one of said pawls being engaged by the ratchettoothed member thatextends into the plunger, and ratchet teeth provided on said frame andengaged by the other of said pawls to prevent retrograde movement of theplunger.

8. An injection syringe comprising a frame that includes a cylinder toreceive a fluid, a plunger extending from the cylinder and being adaptedwhen depressed to eject from the cylinder a dose of the fluid,ratchet-and-pawl mechanism applied to the plunger, said mechanismconsisting of a manually depressible ratchet-toothed member intelescopic relation with the plunger, a ratchet-toothed rack on theframe and pawls on the plunger engaging the ratchet-teeth of said memberand rack, respectively, and means on said frame for guiding said memberand plunger, said mechanism serving totransmit recurrent depressivemovements from said member to the plunger and to prevent return movementof the plunger.

9. An injection syringe comprising a cylinder to receive a fluid, asupport uprising from the cylinder, a spring-return member guided bysaid support and depressible inside it, a series of downturned-ratchetteeth on said member, another series of down-turned teeth on saidsupport, a hollow plunger extending from said cylinder and being asliding fit on said ratchet-toothed mem- 8 ber, and two pawls on saidplunger respectively engaging said two series of teeth, the one pawlserving as a driver between said member and the plunger and the otherpawl serving as a detent for the plunger.

10. An injection syringe comprising a cylinder to receive a fluid, asupport uprising from the cylinder, a bearing at the top of saidsupport, a spring-return member guided by said bearing and depressibleinside said support, a series of down-turned ratchet teeth on saidmember, another series of down-turned teeth on said support, a hollowplunger extending from said cylinder into said support and being asliding fit on said ratchet-toothed member, two pawls on said plungerrespectively engaging said two series of teeth, the one pawl serving asa driver between said member and the plunger and the other pawl servingas a detent for the plunger, and means on said member contactible withsurfaces on said bearing to limit depressive and return movements ofsaid member.

DUNCAN MENZIES McLINTOCK.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,007,471 McCann Oct. 31, 19112,101,140 I-Iege Dec. 7, 1937 2,295,849 Kayden Sept. 15, 1942 2,316,095Mead, Jr. Apr. 6, 1943 2,409,565 Austin Oct. 22, 1946 2,472,116 MaynesJune 7, 1949

